A sinking feeling: NASA prepares for 'maintenance' in
near-Earth orbit

CAPE CANAVERAL, Florida (CNN) -- This is one shuttle mission NASA managers hoped they would not have to fly. Space Transportation System flight No. 101 (which in the befuddling world of shuttle manifesting equates to the 98th flight in the history of the program) is billed as a "maintenance" mission to the near-stillborn International Space Station.

The Russian-built-but-NASA-funded Zarya ("Sunrise") module that left the planet on November 20, 1998, is now out of warranty -- which naturally means things are starting to break. Most notably, the half-dozen 800-ampere batteries that store electrical energy from the solar arrays are draining faster than a six-pack of suds on a hot summer day.

Two of the batteries have failed completely. One is damaged after some recharging problems, and another is operational but degraded.

Like every piece of Russian hardware, the batteries are carbon copies of what is used on The Venerable Space Station Mir, so you might be surprised why these cells aren't going to win any pink bunny awards: Apparently Russian ground controllers were allowing the solar arrays to charge the batteries too fast. You would think they'd know better by now.

In any case, Job No. 1 for the seven-person crew of Atlantis (flight 21 for Orbital Vehicle 104; ISS Mission 2A.2A -- for those of you keeping score at home) will be the installation of four new 163-pound batteries, three of their 34-pound current converters and two 10-pound current converter controllers. The Russians apparently feel bad about this and thus are footing the battery bill. Of course NASA pays the shipping and handling charges (somewhere between $500 million and $1 billion -- excluding taxes, title and dealer prep).

The two-module, embryonic station (a U.S.-supplied docking node called Unity was attached to the station in December of 1998) has some other issues that need attention, not the least of which is that it's falling and it can't get up. Well, actually, in a pinch, it could give itself a boost with the propellant on board Zarya, but mission managers are reluctant to use that fuel.

During the Service Module docking (whenever that may be -- see below), Zarya is the active vehicle (meaning it does all the precise maneuvering). Ground controllers want to preserve enough propellant for multiple docking attempts in case the first automated attempt is a misfire.

So, the Atlantis crew plans to use the orbiter's steering jets to give the station stack a 20-mile-upward nudge.

The launch opportunity (or "window") for all station missions is very narrow (about five minutes). In essence, the shuttle is waiting for the path of the space station's orbit to pass over Cape Canaveral, then launching at precisely the right moment to reach the station, using the least amount of shuttle fuel necessary.

It is kind of like skeet shooting. NASA launch managers must aim at the point where the vehicles will converge -- and then squeeze the trigger at precisely the right time. As it turns out, when the time is right for launch, the station is half a world away.

If they cannot get their act together to launch at the right moment, they will have to wait slightly less than 24 hours for another convergence of Earth, shuttle and station.

Since the space station orbits the Earth every 90 minutes, you might guess that a launch "window" would open up every hour and a half. Not so. While the station orbits at 17,000 mph, the Earth rotates beneath it (about 1,000 mph). As a result, the ground track of the station casts a shadow over the Cape only twice a day. In order to keep the flight and ground crews rested -- and on a reasonable schedule -- NASA chooses to wait a day if they don't squeeze through these tight windows.

But the station's falling altitude makes this intricate game of catch up even more challenging
for the Flight Dynamics team in Houston. To understand their task, think for a moment about a yo-yo. Anyone who's tried that "around-the-world" trick knows the shorter the string, the faster the yo-yo rotates around your finger.

The same goes for a spacecraft orbiting the planet. The lower the orbit, the faster it spins around the Earth.

So Atlantis must fly at a lower altitude than the space station in order to catch up with it. But like that yo-yo, as it has fallen, the space station has picked up speed.

As a result, NASA's rendezvous wizards are finding some days are better than others. The shuttle can catch up with the station by flight day 3 on those better days (May 19 is one of them). But when the launch window opens up on those "other" days, the station will be a little farther from the Cape (May 20 is one of those).

On those days, either NASA would have to live with only a too-tight-for-comfort 3-minute window -- or have the shuttle fire its steering jets to lower its orbit (a "retrograde burn") to pick up some speed while on the way to its meeting with the station. The plan is to do the burn, and even then, Atlantis will still not make it to the station until flight day 4 on those days when the station is farther away.

Regardless of when Atlantis arrives at ISS, the crew will do some work outside before they open the hatches and float over the portals of the station. On flight day 4 (assuming a flight day 3 rendezvous) astronauts Jeff Williams and Jim Voss are on the timeline for a six-hour suited sojourn in the void.

Williams is a space rookie, while Voss is a veteran (three previous flights and one spacewalk under his belt during
STS-69 in 1995). Nevertheless, Williams will sport the coveted red-striped suit of the lead spacewalker (EV-1). So why is the rookie taking the lead?

Here's the deal: When STS-101 was born its special purpose was to stock the cupboards and turn on the lights in the Russian Service Module christened Zvezda ("Star").

Here's a quick fill for those of you who, like me, can't think of anything else but the trials and tribulations of Elian: The Service Module (same basic design as Mir's core module) is the most important Russian contribution to the ISS. Weighing in at 42,000 pounds, it will provide navigation, propulsion, communications, water, power and living quarters for the vanguard long-term crews. Until it is lashed onto the end of Zarya, construction of the sprawling $60 billion outpost will remain at a standstill.

The Russian Zvezda Service Module, scheduled for launch in July

Zvezda sits at the Baikonur Cosmodrome -- now more than two years past its originally promised delivery date. First, a dearth of rubles stalled its construction. Then, last year, the launch gods threw some curve balls: a pair of failures by, of all things, the tried and true, Maytag Launching Machine: the Proton rocket, on whose shoulders Zvezda will ride to low Earth orbit.

The Russians slid to the right all launches by the revered booster while they fixed the problem (metal shavings were being sucked into the combustion chamber). Protons are now back in business.

Which leaves the Russians tinkering with the Service Module software. This is one area where their experience with Mir isn't much help, as the ISS uses those newfangled computers
-- while Mir may as well have been based on a Jules Verne design. Fortunately, Russian software programmers are some of cleverest geeks in the galaxy. Years of coping with very limited hardware made for some ingenious, elegant software solutions. Necessity is the mother of lean code.

The Russians insist they will be ready to fly sometime between July 8 and 14. But after all the missed deadlines, many NASA managers have become apostles of Ronald Reagan, muttering the mantra: "Trust, but verify."

Maybe Zvezda should be renamed "Tolstoy" -- as it is the star of a long, convoluted, turgid tale that seems to never end.

So back now to that spacewalk: When the STS-101 mission plan changed, NASA removed three crewmembers who are experts on stocking-up and spooling-up the Service Module. Astronaut Ed Lu and cosmonauts Yuri Malenchenko and Boris Marukov were politely told their services were no longer needed -- and they were reassigned to a brand new mission (STS-106) that will launch soon after Zvezda joins the ISS stack.

Lu was to be Williams' spacewalking partner. So in January, when Voss dove into Houston's Sonny Carter neutral buoyancy tank to replace Lu, it made sense that the man who hammered out the choreography take the lead. None of this bothers Jim Voss. Not his style.

Williams and Voss have a lot of little chores on their zero-G plates. They will troubleshoot and try to fix a U.S. crane attached to the Pressurized Mating Adapter (onto which shuttles dock with the station). The crane was attached by the last pair of weightless working-stiffs who toiled on the station -- Tammy Jernigan and Dan Barry (STS-96 -- last May/June). But it didn't lock in properly and if there were a breeze up there, it would be flappin' in it.

They will complete assembly of the Russian Strela ("Arrow") crane begun by Jernigan and Barry, replace a faulty antenna on a U.S. communications device, and they will attach some handrails to make things easier on future space hard hats.

The International Space Station (ISS) Shuttle astronauts will try to fix two cranes installed during a May 1999 mission

When the crew opens the hatch and enters the ISS, their first order of business is to check the air in there. During
STS-96, some of crewmembers didn't feel so hot after stints working in Zarya. But in an unfortunate case of misguided white-scarf, astro-machismo, they never 'fessed up during the mission -- even during private channel chats with flight surgeons.

This has caused no small amount of heartburn at the Mission Operations Directorate in Houston. Had the crew been more forthright, engineers would have devised a systematic plan for diagnosing the problem during the mission. But since the crew waited until it was time for post flight
de-briefings to mention their maladies, doctors and engineers were left to do something they loathe: speculate.

Their best guess on the culprit: carbon dioxide. Quite simply: the crew might have been inhaling too much of their own breath. As it is, air doesn't circulate very well in microgravity, but on Zarya the problem appears to be more acute. This is exacerbated when astronauts crowd the module and open up panels and doors, further impeding the air flow. We are told this is not a long term problem, that Zvezda is equipped to do the air handling for the station with much more efficacy.

In any case, the 101 crew will carry around small, portable fans and carbon dioxide alarms as they take air samples, measure the air flow, modify the ducts, replace air filters, and above all, come clean in their confabs with the flight surgeons.

For her part, Atlantis isn't the orbiter she used to be. She is much better after a three-year flight hiatus -- much of that time spent at the space shuttle equivalent of the Canyon Ranch, Boeing's Palmdale plant. That's where orbiters visit periodically for the self-improvement and weight-loss campaign NASA calls OMDP (Orbiter Maintenance Down Period).

More than 100 modifications were made during Atlantis' OMDP. The airlock was moved into the payload bay so that Atlantis can dock with ISS, the communication system was upgraded, a lot of weight was trimmed, the cooling system upgraded, and the cabin floor was strengthened.

But the most visible "mod" is the facelift on the flight deck. Thirty-two mechanical gauges and four monochromatic cathode ray tubes were replaced with 11 full-color flat-panel displays. NASA calls it the Multifunction Electronic Display (MEDS) but most pilots simply know it as a "glass cockpit." This technology has been used on commercial airliners for several years, and now, after a $200 million research and development effort, it's ready for space flight.

By 2002, all four orbiters in the shuttle fleet will sport glass cockpits (Columbia is in the midst of her Palmdale facelift right now). As it stands right now, the glass cockpit screens depict the old "steam gauges" in full color. So it is the same information, just easier to manipulate and understand.

Once all the cockpits are upgraded, NASA will begin changing the way the data is presented -- offering the flight crew some more intuitive graphical displays. An arcane series of numbers and compass headings might be transformed into a simple graphical display of a shuttle, the Earth, and flight path. The "smart cockpits" will be introduced in 2005.

Before long, NASA might be doing its recruiting for shuttle pilots at video game parlors.